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Controlled Ambipolar-to-Unipolar Conversion in Graphene Field-Effect Transistors Through Surface Coating with Poly(ethylene imine)/Poly(ethylene glycol) Films

Authors

  • Zheng Yan,

    1. Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005, USA
    2. Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main Street, Houston, TX, 77005, USA
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  • Jun Yao,

    1. Applied Physics Program through the Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX, 77005, USA
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  • Zhengzong Sun,

    1. Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005, USA
    2. Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main Street, Houston, TX, 77005, USA
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  • Yu Zhu,

    1. Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005, USA
    2. Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main Street, Houston, TX, 77005, USA
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  • James M. Tour

    Corresponding author
    1. Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005, USA
    2. Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main Street, Houston, TX, 77005, USA
    3. Applied Physics Program through the Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX, 77005, USA
    4. Department of Mechanical Engineering and Materials Science, Rice University, 6100 Main Street, Houston, TX, 77005, USA
    • Department of Chemistry, Rice University, 6100 Main Street, Houston, TX, 77005, USA.

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Abstract

A controlled ambipolar-to-unipolar (n-type) conversion, along with a maximum fourfold increase in the electron mobility, in graphene field-effect transistors (FETs) is achieved by coating the surface of graphene with a layer of a mixed polymer system, poly(ethylene imine) (PEI) in poly(ethylene glycol) (PEG). The PEG serves as a physisorption adhesion agent for the PEI. Both unipolar and ambipolar n-type doping can be realized by adjusting the thickness of PEI films atop the graphene channel. The observed phenomena are attributed to the doping/dedoping effects of the external PEI film. The study provides a guide to engineering graphene transport properties through chemical modifications.

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